I think that it is safe to say that most people operate under the assumption, "if I did nothing wrong, then there is no reason for me to speak with the police without the assistance of an attorney." Frequently, however, this simply is not the wise thing to do.
The first reason why you shouldn't speak to the police without the presence of an attorney is: just because you don't believe you have violated the law doesn't mean that you haven't. In short, there are hundreds of criminal laws enforced in the Commonwealth of Pennsylvania and it is doubtful that you know what all of them are. And since Ignorance of the law is no excuse for breaking the law, it's really not a good idea to agree to be interviewed by the police unless you speak with a criminal attorney first.
The second reason why you shouldn't speak to the police without having an attorney present is that it is not an equal playing field between you and the police during an interrogation. During the interview the police are permitted to lie to you about the facts of the case, the evidence they have, the number of witnesses they have spoken to etc. On the other hand, if you lie to the police, then you have broken the law and can be charged with a misdemeanor crime. The police, depending on the case, may even utilize intimidation methods during the interview. One officer may raise his voice and scream at you and attempt to physically intimidate you during the interrogation. This is especially true if the interview is not being recorded. Determining what your rights are during police contact
Finally, studies show that people sometimes confess to crimes that they did not commit simply because police use the aggressive interrogation techniques discussed above.
The criminal justice system is not something to be taken lightly. If you are being investigated about a crime, contact an experienced criminal lawyer immediately. Aggressive Criminal Lawyers